Pre-fire Treatment Effects and Understory Plant Community Response on the Rodeo-chediski Fire, Arizona

High severity wildfires have been increasing across southwestern ponderosa pine forests in recent decades. As the effects of wildfire become more widespread across the landscape, the need for information about the ecological effects of fire on understory vegetation is mounting. We investigated understory plant community response to the Rodeo-Chediski fire by conducting parallel studies on the White Mountain Apache Tribal lands (WMAT) and the Apache-Sitgreaves National Forests (A-S). We estimated plant canopy cover by species and quantified total plant species richness on 1000m2 plots. We established 71 plots on WMAT lands. Plots were stratified by fire severity (low and high) and pre-fire treatment (cut/burned and untreated). We found significantly higher plant cover on areas that were burned by severe fire, but did not detect significant differences due to pre-fire treatment. There was no significant difference in cover of exotic species between high and low severity sites. Indicator species were primarily early successional species or species that were included in the post-fire seed mix. We established 84 plots on the A-S. This study consisted of 7 paired stands of treated (pre-fire fuel reduction) and untreated sites. These sites had been established by the USDA Forest Service in 2002 after the fire to assess effectiveness of fuel-reduction treatments in altering fire behavior. We found significantly higher plant cover on areas that had not been treated, and had therefore burned with higher severity. There was no 2 significant difference in cover of exotic species between treated and untreated stands. Indicator species were primarily early successional species or species that were included in the post-fire seed mix. In both studies we found a limited response of exotics, which is surprising given the history of active management by both land agencies. Other studies have shown higher exotic species presence following severe wildfires in areas with histories of active management that included practices such as logging, grazing, and seeding. The pre-fire plant community must not have had large populations of exotic species, despite past management practices to result in a native-dominated post-fire community. Whether the few exotic species we observed, including a number of species seeded following the fire, persist and spread in the post-fire plant community remains to be seen